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A211083
1/4 the number of n X n 0..3 symmetric matrices with every element equal to two or three horizontal and vertical neighbors
0
0, 1, 0, 12, 18, 624, 6012, 228984, 8210664, 619049280, 63783422784, 11382530540616
OFFSET
1,4
EXAMPLE
Some solutions for n=6
..1..1..1..1..1..1....2..2..1..1..0..0....2..2..0..0..1..1....0..0..3..3..1..1
..1..3..3..1..1..1....2..2..1..1..0..0....2..2..0..0..1..1....0..0..3..3..1..1
..1..3..3..1..2..2....1..1..2..2..3..3....0..0..1..1..2..2....3..3..2..2..1..1
..1..1..1..1..2..2....1..1..2..2..3..3....0..0..1..1..2..2....3..3..2..2..1..1
..1..1..2..2..0..0....0..0..3..3..2..2....1..1..2..2..0..0....1..1..1..1..2..2
..1..1..2..2..0..0....0..0..3..3..2..2....1..1..2..2..0..0....1..1..1..1..2..2
CROSSREFS
Sequence in context: A212128 A110932 A112880 * A100541 A337424 A056688
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 31 2012
STATUS
approved